Starting system for a gas-turbine installation

ABSTRACT

A gas-turbine installation having a pressurized-air hot-gas generator in which a fuel is reacted with the pressurized air, has a high-pressure turbine-driven compressor and a low-pressure turbine-driven compressor in tandem to supply the compressed air for the gasifier, the turbines being operated by the expanding combustible gases from the gasifier. One or both of the turbines may be provided with electrical generators and/or with starting motors and a steam-generating cycle may be provided for operation by the heat of the combustible gases. The starting system of the invention includes a compressed-air reservoir adapted to be charged by one or both of the compressors during normal operation of the system and capable of stirring a volume of air under such pressure that, for starting the system, the gasifier may communicate with the reservoir to generate sufficient hot combustion gases to drive the turbine.

United States Patent Bruns 1 Dec. 5, 1972 [541 STARTING SYSTEM FOR AGAS- 2,706,150 4/1955 Lloyd ..60/39.l2

TURBINE INSTALLATION FOREIGN PATENTS OR APPLICATIONS [72] Inventor:Paul-Heinz Bruns, Mulheim, Germany 1121,455 3/1956 Germany ..60/39.l2

[73] Assignee: Steinkohlen-Elektrizitat Aktienprimary E i c lt c lgesellschafi, ESSeH, Germany Assistant Examiner Warren Olsen J 25Attorney-Karl ROSS [21] mm 109,358 57 ABSTRACT vA gas-turbineinstallation having a pressurized-air hot Foreign Appllcatlon PriorityData gas generator in which a fuel is reacted with the pres- Feb 7 1970Germany P 20 05 722 l surized air, has a high-pressure turbine-drivencomp pressor and a low-pressure turbine-driven compressor [52] U.S. Cl...60/39.l8 B, 60/39.l2 60/39.]4 in tandem Supply the mPressed thegasifi' 511 lm. Cl ..F02c 1/04, F02c 5/08, F02c 5/12 P bemg peratfed byexpandmg [58] Field of Search 60/39 12 39 18 B 39 I 4 bustible gasesfrom the gasifier. One or both of the 39'25 turbines may be providedwith electrical generators and/or with starting motors and asteam-generating cycle may be provided for operation by the heat of the[56] References Clte d combustible gases. The starting system of theinven- UNITED STATES PATENTS tion includes a compressed-air reservoiradapted to be h charged by one or both of the compressors during nor-Parmegiam BI al ma] operation of the ystem and capable of tirring a2,357,041 8/1944 Woolley ..60/39.18 B volume f i under h pressure that,f starting h Traupcl ystem the gasifier may communicate the reser, 5 :1voir to generate sufficient hot combustion gases to 1n er et a d i th tbi 2,632,297 3/1953 Ogston ..60/39.l2

' LOW-PRESSURE COHP/PEsIo/t H! CH 'FEESYURE C OHPRESSOR GENEE/JTOE 7Claims, 1 Drawing Figure PATENTED 5 3,704,586

PRESSURIZED AI? 2 GAS/FIEE H 1 6H PEES 'URE COMPRESSOR l GENERATORCONDENSER 78a couosnsn rs PUMP 7 9 8 75 /8c GENEIZATOE LOW-PRESSUEECOMPRESSOR Attorney STARTING SYSTEM FOR A GAS-TURBINE INSTALLATION FIELDOF THE INVENTION starting or bringing into operation a gas-turbine l0generating plant.

BACKGROUND oF THE INVENTION In a gas-turbine generating plant, one ormore combustors or gasifiers are supplied with fuel which reacts withoxygen, eg. from the air, to produce a produce a rapidly expandingstream ,of high-pressure hot gases.

The gases are supplied to one or more expansion turbines which can becoupled to-electrical generators or motor-generator sets and generallyare also connected to compressors for supplying air under pressure tothe combustor. Startup of the installation is generally effected by theuse of motor-generator sets coupled to the turbine shafts and/or thecompressorst'hereof such that the motors are energiied to drive theturbines which, in turn, drive the compressors, the latter supplying airto the gasifier, so that the combustion gases may, in turn, take overthe work-performing function.

Such systems have a disadvantage in that an electrical failure, absent asource of standby power, prevents energization of the starting motorsand hence prevents the installation from being started. Complex systemsmust be provided to constitute the stnadby-energy source or to protectthe motors against failure. In practice, one avoids the difficultiesinherent in starting the installation while maintaining it in operationeven when shut-down may be economically practical.

OBJECTS OF THE INVENTION It is an important object of the presentinventionto provide an improved starting system for a gas-turbineinstallation. V v A It is another object of our invention to provide agas turbine electricity-generating plant with improved starting means.

An object of the invention also resides in the provision of an improvedgas-turbineplant.

SUMMARY OF THE INVENTION A gas-turbine installation according to thepresent invention comprises a pressurized air gasifier in which a fuel,preferably coal, is reacted with the oxygen contained in high-pressureair to form gaseous combustible products, hereinafterreferred to ascombustion gas. The combustible gas, according to the present invention,is applied to at least one gas turbine to drive at least one electricgenerator and at least one compressor which communicates with thegasifier to deliver compressed air at high pressure to the latter.According to the principles of the present invention, a compressed- 1 tothe gasifier to supply thepressurized air required for the initialformation of the combustible gases to drive the turbine.

According to an important feature of this invention, the turbine isconnected in series with a steam-generating plant so that residual heatof the combustible gases is used at least in part to convert water tosteam in a substantially closed cycleand operate a steam genera: torcontributing to the electrical output of. the plant. A boiler may serveas the coupling means between the steam circuit and the gas-turbinecircuit.

According to the principles of the present invention, the hot combustiongases are applied to the turbine of a high-pressure compressorcommunicating selectively with the compressed-air reservoir and thepressurizedair gasifier and with an electrical generator. In tandem withthe high-pressure compressor is a low-pressure or precompressor whichmay be coupled with the main electricity-generating unit and is drivenby the combustion gases via a second gas turbine, the combustion gasesbetween these gas turbines traversing the aforementioned boiler. Atleast the high-pressure compressor is provided with a motor, preferablyin theform of a motor generator to supply auxiliary compressed air tothe gasifier should the compressed-air reservoir be depleted before thegas-turbine installation has developed full-running characteristics..Another motor may be coupled with the low-pressure compressor.

"Among the advantages of the system described above is the low startingtime inasmuch as theimmediate availability of the pressurized air at thegasifier and the immediate capability of the latter to producehigh-pressure combustible gases, bring the expansion turbine stages upto full speed'rapidly and permits the compressors to take over the airsupply when the compressed air reservoir is depleted.

Means is provided for connecting the pressurized-air reservoir to thepressure-side of the high-pressure compressors between the latter andthe gasifier so that a portion of the compressed air supplied by thehighpressure compressor is diverted into the compressedair reservoir torecharge the latter during normal use. Since the compressed airreservoir is always available during standstill, no special measures arerequired before starting.

According to another feature of this invention, an auxiliary compressor,driven by a power source independent of the gas-turbine generatingsystem, e.g. an electric motor, is connected to the compressor. While Iprefer to pressurize the compressed-air tank solely with thehigh-pressure fluid derived from the high-pressure v compressorconnected with the first-stage turbine, I

may nevertheless use exclusively the auxiliary compressor or motor toprovide the stored energy, in the form of compresses air, which is toserve as the initial driving force on starting. Where most of the outputof the highpressure compressor may have to be delivered to the gasgenerator upon large electrical demands developing on the generatingsystem, I may use the auxiliary motor and compressor as an added sourceof compressed air for the reservoir. I

While I refer to a single pressurized-gas coal gasifier, it should beunderstood that a plurality of such gasifiers may be used to feedcombustible gases to a single expansion turbine or to respectiveexpansion turbines operating in parallel. In this case, I prefer todimension the compressed air reservoir to that which can'operate all ofthe gasifiers simultaneously. A system of this type DESCRIPTION OF THEDRAWING The above and other objects, features and advantages of thepresent invention will become more readily apparent from the followingdescription, reference being made to the accompanying drawing in whichthe sole FIGURE is-a flow diagram illustrating the invention.

SPECIFIC DESCRIPTION In the drawing, I show a pressurized-air coalgasifier l which discharges into an expansion turbine 2 coupled by ashaft. 15 to a high-pressure compressor 3, the pressure side of which isconnected at 3a to an inlet of the combustor 1. The partially depletedcombustible gas is fed at 2a into a boiler 5, constituting part of asteam generating circuit and thereafter passes at 5a into a furtherexpansion turbine 6 which is coupled by the shaft 15a with the mainelectric generator 9, with a lowpressure compressor 7 anda startingmotor 8 which may be connected with the compressor by a clutch 8a.

Ambient air is supplied at substantially atmospheric pressure via line20 to the low-pressure compressor 7 and thereupon passes through a heatexchanger-18 ahead of the'high-pressure compressor 3.

The steam-generating circuit comprises a steam turbine 10 driving anelectric generator 11 and connected in series with the coils of theboiler 5. condenser-heatexchanger 18a lies in series with the turbine 10together with a condensate pump 18b. A heater 180 is provided to heatthe liquid which is circulated through the boiler 5. The heat suppliedat 180 is the residual heat carried by the combustion gases emergingfrom the turbine 6 and conducted through the heat exchanger 18c isrepresented by line 21.

A motor-generator set 4 is mechanically coupled with the turbine 2 by ashaft 15b and is consequently connected with the compressor 3 to enableit to drive the turbine 2 and the compressor 3 in its motor mode ofoperation.

A compressed-air reservoir 12' is connected via a valve 17b to thecombustor 1 and is, moreover, connected to the outputside of thecompressor 3 by a twoway valve 170 which distributes compressed air fromthe high-pressure compressor 3 to either the gasifier 1 'or thecompressed-air tank 12. Charging of the combetween the high-pressurecompressor 3 and the gasifier 1. To prevent damage to the expansionturbine, as may result from corrosive components of the combustion gas,a gas washer 19 is provided in series with the gasifier l and theexpansion turbine 2. A further valve 17d controls the rate of feed ofthe combustion gases to the expansion turbine 2 and yet another valvel7e permits air from the low-pressure compressor to be bled to theboiler 5 for combustion of the gases therein.

An important feature of this invention resides in the provision of acompressed-air storage vessel 12 which contains sufficient compressedair to operate all of the gasifiers 1 for a period sufficient to allowthe compressor 3, in tandem with the low-speed compressor 7, to supplysufficient air to operate the gasifiers. When this occurs, theinstallation can be switched over from its idle condition to its normalpower state.

OPERATION AND SPECIFIC EXAMPLE The turbine installation illustrated inthe drawing of course operates in accordance with conventionalprinciples for the starting technique which is unique to the presentinvention. Consequently, the operation may be described with respect toa specific Example which is intended to be merely illustrative.

With the gas-turbine installation of the drawing in its inoperativestate, 400 m of compressedair is stored in the tank 12 at 36 atmospheresgauge and ambient temperature. To start the system, 30,000 m per hour(STP) of compressed air is discharged via valve 17b into the gasifierlin which powdered coal is re-formed into a combustible gas at 19atmospheres absolute and a temperature of 200C, after washing at 19. Thecombustible gas is supplied at 79.5 kg/sec to the expansion turbine 2and has a heat content of 1320 Kcal/kg.

The combustible gases containing carbon monoxide and emerging from theexpansion turbine 2 are led at a pressure of 9.62 atmospheres absoluteand a temperature of 162C to the boiler 5 as a fuel gas. This fuel gashas a sensible heat content of 340 Kcal/kg and is supplied at a rate of79.5 kg/sec. The'fuel gases burned in the boiler'5 with 284.1 kg/sec ofoxygen supplied via valve 17e from the low-pressure compressor 7 toproduce an exhaust gas at 5a at a pressure of 9.5 atmospheres absolute,300 Kcal/hourand a temperature of 804C at a rate of 363.6 kg/sec. Theexpansion turbine 6 is driven with this exhaust gas to produce adepleted gas at a temperature of 399C and a heat content of 1078 Kcal/kgwhich is delivered to the heatexchanger 180 of the steam cycle. Thefinal exhaust gas has a heat content of only 26.6 Kcal/kg and can bedisposed of at 21.

The superheated steam derived from the boiler S at a pressure ofatmospheres absolute, a temperature of 525C and a rate of 340 metrictons/hour is used to drive the steam turbine 10 which operates the powergenerator 11 at an output of 96 megawatts.

The low-pressure compressor 7, driven by the turbine 6 is supplied withambient air at 20 at a temperature of 15C, a pressure of 760 ton and ata rate of 340 kg/sec. During startup, the motor 8 may be operated at 2.2megawatts at a speed of 600mm to provide lowpressure air to thecompressor 3 while the latter is driven by the air from tank 12, via thegasifier, etc. A major contribution of 74 megawatts is provided by thegenerator 9 driven by the gas turbine 6.

The low-pressure air delivered via a heat exchanger 18 to the compressor3 has a temperature of 307C and a pressure of 9.62 atmospheres/gauge andis operated at a rate of 340 kg/sec. The output from the high-pressurecompressor 3 consists of air at a pressure of 22 atmospheres gauge and atemperature of 225C which is supplied with a heat content of 54.5Kcal/kg at a rate of 35.4 kg/sec. The motor generator 4 which maycontribute start torque to the compressor 3 has a speed of 3000 rpm andconsumes 1.8 megawatts when operated as a starting motor to assist thecompressed air from tank 12. After starting, it functions as a generatorto produce 0.445 megawatts. During nonpeak periods, the compressor 3 orthe compressors 13, connected to the electrical output of theinstallation, pressurizes the tank 12 so that the compressed air isavailable at the time of the next starter. 1

The improvement described and illustrated is believed to admit of manymodifications within the ability of persons skilled in the art, all suchmodifications being considered within the spirit and scope of theinvention except as limited by the appended claims.

We claim:

1. A gas-turbine electricity-generating installation, comprising: i

a. a pressurized-air fuel gasifier for producing a highpressurecombustible gas stream;

b. a high-pressure turbocompressor driven by said high-pressurecombustible gas stream and discharging a low-pressure combustible gasstream while supplying high-pressure compressed air to said gasifier;

c. a boiler connected to said high-pressure turbocompressor and heatedby the combustion of said low-pressure combustible gas stream forgenerating high-pressure steam and discharging a waste gas;

d. a steam-driven electrical generator connected to said boiler andoperated by the high-pressure steam therefrom to produce electricity;

e. a low-pressure turbocompressor driven by said waste gas for supplyinglow-pressure air to said high-pressure turbocompressonand f. means forstarting said installation and including a compressed-air reservoir of apressure-and-volume capacity sufficient to operate said gasifier in' theabsence of air from said high-pressure turbocompressor for a periodsufficient to permit the combustible gases from said gasifier to drivesaid highpressure turbocompressor,

means for connecting said reservoir to said gasifier for starting saidinstallation, and

means for charging said reservoir with compressed air.

2. The installation defined in claim 1, further comprising:

g. a starting motor connected with said low-pressure turbocompressor andoperable concurrently with the supply of compressed air from saidreservoir to said gasifier.

3. The installation defined in claim 2 wherein the means for chargingsaid reservoir with compressed air includes means for connecting theoutput of said highpressure turbocompressor with said reservoir.

4. The installation defined in claim 2 wherein said means for chargingsaid reservoir. with compressed air includes a furt er compressor drivenby a motor supplied with electrical energy from a source independent ofthe installation.

5. The installation defined in claim 2, further comprising:

h. an electrical generator coupled with said low-pressureturbocompressor and driven by said waste gas.

6. The installation defined in claim 5, further comprising:

i. means for preheating the feed to said boiler with the waste gasemerging from said low-pressure turbocompressor.

7. The installation defined in claim 6, further comprising:

j. a motor generator connected to said high-pressure turbocompressor.

1. A gas-turbine electricity-generating installation, comprising: a. apressurized-air fuel gasifier for producing a high-pressure combustiblegas stream; b. a high-pressure turbocompressor driven by saidhigh-pressure combustible gas stream and discharging a low-pressurecombustible gas stream while supplying high-pressure compressed air tosaid gasifier; c. a boiler connected to said high-pressureturbocompressor and heated by the combustion of said low-pressurecombustible gas stream for generating high-pressure steam anddischarging a waste gas; d. a steam-driven electrical generatorconnected to said boiler and operated by the high-pressure steamtherefrom to produce electricity; e. a low-pressure turbocompressordriven by said waste gas for supplying low-pressure air to saidhigh-pressure turbocompressor; and f. means for starting saidinstallation and including a compressed-air reservoir of apressure-and-volume capacity sufficient to operate said gasifier in theabsence of air from said high-pressure turbocompressor for a periodsufficient to permit the combustible gases from said gasifier to drivesaid high-pressure turbocompressor, means for connecting said reservoirto said gasifier for starting said installation, and means for chargingsaid reservoir with compressed air.
 2. The installation defined in claim1, further comprising: g. a starting motor connected with saidlow-pressure turbocompressor and operable concurrently with the supplyof compressed air from said reservoir to said gasifier.
 3. Theinstallation defined in claim 2 wherein the means for charging saidreservoir with compressed air includes means for connecting the outputof said high-pressure turbocompressor with said reservoir.
 4. Theinstallation defined in claim 2 wherein said means for charging saidreservoir with compressed air includes a further compressor driven by amotor supplied with electrical energy from a source independent of theinstallation.
 5. The installation defined in claim 2, furthercomprising: h. an electrical generator coupled with said low-pressureturbocompressor and driven by said waste gas.
 6. The installationdefined in claim 5, further comprising: i. means for preheating the feedto said boiler with the waste gas emerging from said low-pressureturbocompressor.
 7. The installation defined in claim 6, furthercomprising: j. a motor generator connected to said high-pressureturbocompressor.